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photo_image_overlay

Image Overlay — Composite one image on top of another at a specified position. Takes two separately-named uploads: 'background' and 'overlay'. [category: photo]

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
scaleNoOverlay size as a percent of the overlay's own size, not of the background: 100 keeps it as it is, 50 halves it, 200 doubles it.
opacityNoOverlay opacity 0-100.
overlayYesImage composited on top — JPG, PNG, WebP, BMP (max 20MB)
positionNoAnchor cell the overlay snaps to; x_offset/y_offset shift from THIS anchor, not from the top-left corner.mc
x_offsetNoPx shift with gravity semantics: positive pushes inward from the anchored edge (leftward from right-side anchors).
y_offsetNoPx shift with gravity semantics: positive pushes inward from the anchored edge (upward from bottom anchors).
backgroundYesBase image — JPG, PNG, WebP, BMP (max 30MB)
output_formatNoOptional output format; defaults to the background's format.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed6 schema fields changed
    • addedInput schema / properties / opacity / x-ui / draw
      Added value: +{
+  "max": 100,
+  "of": "overlay",
+  "role": "opacity"
+}
    • addedInput schema / properties / position / x-ui / draw
      Added value: +{
+  "cells": {
+    "bc": "bc",
+    "bl": "bl",
+    "br": "br",
+    "mc": "mc",
+    "ml": "ml",
+    "mr": "mr",
+    "tc": "tc",
+    "tl": "tl",
+    "tr": "tr"
+  },
+  "of": "overlay",
+  "role": "anchor"
+}
    • addedInput schema / properties / scale / x-ui / draw
      Added value: +{
+  "measure": "percent-own",
+  "of": "overlay",
+  "role": "size"
+}
    • addedInput schema / properties / x_offset / x-ui / draw
      Added value: +{
+  "from": "inward",
+  "of": "overlay",
+  "role": "offset_x"
+}
    • addedInput schema / properties / y_offset / x-ui / draw
      Added value: +{
+  "from": "inward",
+  "of": "overlay",
+  "role": "offset_y"
+}
    • addedInput schema / x-draw
      Added value: +{
+  "overlay": {
+    "image": "overlay",
+    "noun": "overlay",
+    "on": "background",
+    "shape": "stamp",
+    "title": "Where the overlay goes"
+  }
+}
  2. Changed3 schema fields changed
    • addedInput schema / properties / x_offset / x-ui / pair_joint
      Added value: +","
    • addedInput schema / properties / x_offset / x-ui / pair_label
      Added value: +"Nudge from the anchor"
    • addedInput schema / properties / x_offset / x-ui / pair_with
      Added value: +"y_offset"
  3. Changed1 schema field changed
    • changedInput schema / properties / scale / description
      Previous value: -"Overlay width as a percent of background width, 1-200."New value: +"Overlay size as a percent of the overlay's own size, not of the background: 100 keeps it as it is, 50 halves it, 200 doubles it."
  4. Changed1 schema field changed
    • addedInput schema / properties / output_format / x-ui
      Added value: +{
+  "unset_label": "Keeps background's format"
+}
  5. Changed4 schema fields changed
    • addedInput schema / properties / opacity / x-ui
      Added value: +{
+  "unit": "%"
+}
    • addedInput schema / properties / scale / x-ui
      Added value: +{
+  "unit": "%"
+}
    • addedInput schema / properties / x_offset / x-ui
      Added value: +{
+  "unit": "px"
+}
    • addedInput schema / properties / y_offset / x-ui
      Added value: +{
+  "unit": "px"
+}
  6. Changed1 schema field changed
    • addedInput schema / properties / output_format / enum
      Added value: +[
+  "jpg",
+  "png",
+  "webp",
+  "bmp"
+]
  7. First observed

TDQS

A3.5/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=false) already signal this is a non-destructive local transformation, so the description's job is lighter. It adds little beyond that: it doesn't discuss output behavior, size/format constraints, or limits, relying mostly on the schema and annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences that front-load the core action and then clarify the two-upload structure. The trailing '[category: photo]' tag is minor metadata clutter rather than useful content, keeping it from a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an 8-parameter image transform with full schema coverage and no output schema, the description conveys the essential concept and input model adequately. It doesn't explain return/output framing, but with no output schema and rich parameter docs, that is a minor gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so every parameter including position, scale, offsets, opacity, and formats is already well documented. The description only echoes the two upload names ('background' and 'overlay'), adding no meaning beyond the schema. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Composite) and resource (one image on top of another) with the notion of a specified position, which clearly conveys what the tool does. It does not explicitly differentiate itself from near-neighbors like photo_watermark or media_add_watermark, so it stops short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage through the compositing framing and the note that it takes two separately-named uploads, but it never states when to prefer this over photo_watermark, photo_collage, or the other image tools. No explicit when/when-not or alternatives are given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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